Small-scale ionospheric structures associated with mid-latitude spread-F |
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| Institution: | 1. Department of Earth and Planetary Sciences, Kyushu University, 744 Motooka Nishi-ku, Fukuoka, Japan;2. National Institute of Geophysics, Geodesy and Geography, Bulgarian Academy of Sciences, Sofia, Bulgaria;3. National Institute of Information and Communications Technology, Tokyo, Japan;4. Faculty of Science and Technology, Seikei University, Tokyo, Japan;1. Utah State University, Logan, UT, 87545, USA;2. University of Colorado at Boulder, Boulder, CO, 80302, USA;3. Delft University of Technology, Delft, The Netherlands;4. National Centre for Space Studies (CNES), Toulouse, France;1. Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand;2. Space Environment Laboratory, National Institute of Information and Communication Technology, Nukuitita, Koganei, Tokyo 184-8795, Japan;1. Institute of Meteorology and Oceanography, PLA University of Science and Technology, Nanjing 211101, China;2. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China;3. State Key Laboratory of Space Weather, Chinese Academy of Sciences, Beijing 100190, China;1. National Atmospheric Research Laboratory, Gadanki 517 112, Pakala Mandal, Chittoor District, Andhra Pradesh, India;2. Indian Institute of Space Science and Technology, Valiamala P.O., Thiruvananthapuram 695 547, Kerala, India |
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| Abstract: | Slant-F traces on ionograms recorded by a modern ionosonde in a sunspot-minimum period have revealed the existence of field-aligned irregularities at times of spread-F occurrence. This appears to be the first investigation in a mid-latitude region around 36° (geomagnetic) to detect these irregularities at F2-region heights using an ionosonde. Although such traces were observed frequently near sunspot minimum they were seldom recorded for periods close to sunspot maximum. Also, for a specific spread-F event in August 1989, both the ionograms from the modern ionosonde and scintillations of 150 MHz transmissions from a Transit satellite indicate the existence in the ionosphere of periodic structures (period around 11 min). The scintillation recording also included rapidly fading signals indicative of small-scale structures. The satellite had a path close to the magnetic meridian which passed through the recording station (Brisbane, Australia). Because of the enhanced signal fluctuations in the scintillation recording on this occasion it seems likely (with the support of other evidence on the ionograms) that the small-scale structures present were field-aligned. |
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